The present invention relates generally to semiconductor device processing and, more particularly, to removing cured and uncured organic polymers used as low-k dielectrics in semiconductor structures.
In the fabrication of integrated circuit devices, it is often desirable to isolate individual components of the integrated circuits from one another with insulative materials. Such insulative materials may include, for example, silicon dioxide, silicon nitride and undoped silicon. While these materials may have acceptable insulating properties in many applications, they also have relatively high dielectric constants, which can lead to capacitive coupling between proximate conductive elements. This is particularly disadvantageous, given the ever-decreasing distances between conductive circuit elements, and the use of multi-layered structures. An unnecessary capacitive coupling between adjacent wires increases the RC time delay of a signal propagated therethrough, resulting in decreased device performance. Thus, for specific applications, insulating materials having relatively low dielectric constants (e.g., κ<3) are desired.
Certain organic polymers are known in the semiconductor manufacturing industry for their “low-k” dielectric properties, which polymers are often used for intermetallic insulation in damascene structures. An example of one such polymer is SiLK®, manufactured by The Dow Chemical Company. SiLK® is typically applied to semiconductor wafers by spin-on coating in a wafer track, similar to the process used in the application of photolithography resist. Initially in liquid form during the spin-on coating, the SiLK® material dries quickly after the coating, thereby creating peaks and valleys of topography as it blankets device features having distinct step heights.
However, as is the case with other process operations, the possibility exists that the application of a spin-on polymer, such as SiLK®, is carried out incorrectly for a variety of possible reasons (e.g., equipment malfunction or human error). Thus, in order to salvage valuable semiconductor wafers, it is economically desirable to have a functional rework process that fully removes the dielectric coating without eroding any underlying films on the wafer.